Making service provisioning significantly more sustainable is crucial if humankind wants to make a serious effort to operate withinthe boundaries of what the planet can support. The purpose of this paper is to develop a systemic understanding of sustainability inservice provision and shed light on the mechanisms that drive unsustainability and hinder service providers in their efforts to bemore sustainable. To contextualize our study, we focus on a significant sustainability problem: food waste stemming from foodretail at the retailer-consumer interface. We make two theoretical contributions to the service research on sustainability. First, weoffer a systemic conceptualization of sustainability in service as a dynamic ability of a focal system (e.g., a servicefirm) to sustain thesystem(s) that contains it. Second, we explicate the mechanisms—stocks andflows, feedback and mindsets—that contribute to(un)sustainable service provision as a systemic behavior, and which can thus be used as intervention points when designingsustainability initiatives. Our work also has significant practical implications for food retailers and policymakers working towardsreaching UN’s Sustainable Development Goal 12.3, as we specify the feedback loops that drive food waste and hinder efforts toreduce it at the retailer-consumer interface.